Corrosion-resisting metal



July 27 1926.

1,594,061 0. E. JONES CORROSION RESISTING METAL Filed June 19, 1922 Fig! ea eamzeaezezezee COLORED METAL His Attorney.

Patented July 27, 1926.

UNITED STATES PATENT O F- CE:-

CHARLES E JONES, OF SCHENECTADY, NEW YORK, ASSIGNOB TO GENIERLII] ELECTRIC COMPANY, A. CORPORATION OF NEW YORK. I

GORROSION-BESISTDTG' METAL.

Application filed June 19, use. Serial no. 568,485.

The present invention relates to theprof duction of a protective coating-on nonferrous metals, subject to corrosion and in particular aluminum and magnesium and their various alloys.

The light non-ferrous metals aluminum and magnesium, either pure or alloyedwith each other, or with copper, zinc, silicon or other metals, although relatively permanent in dry air, under some conditions are subject tocorrosion, particularly when exposed to, moist salt air. The protection of these metals by painting, enameling or varnishing,

- is not adequate because these coatings are apt to crack and peel off, and will in time expose the foundation metal. Attempts heretofore made to plate these metals by electrolytic deposition of metals which resist corrosion, as for example, copper, nickel,

these platings through their electrolytic potential difi'erence to aluminum or magnesium have accelerated the corrosion. The

2 galvanic action between. the plate and the mium are highly resistant to corrosion in a.

salt atmosphere.

.The accompanying drawing shows in Fig. 1 a magnified cross-section of a sheet of aluminum coated with cadmium, and Fig. 2 is a cross-section of a similar article with the additional provision of an exterior film of coloring metal.

In carrying out my invention, the article to be coated is first cleaned by cleaning methods so well understood that they, require no description here on my part. The cleaned article is coated with cadmium in any suitable way, preferably by electrolysis. For example, it is made the cathode in an electrolytic bath containing a cadmium zinc, tin, brass, etc., have failed, and in fact,

underlying metal, which occurs when the or t e hydroxide, and containing also p0 tassium or sodium cyanide. The anode may.

consist of cadmium or carbon. I may use from 1 to 4 ounces of cadmium compound, and 2 to 5 ounces of cyanide in a gallon of solution, and proceed otherwise by approvedmethods of electrolysis. I may also use an acid bath-containing, for example, cadmium sulphate and sulphuric acid. I may use for compound, such as'the chloride, the sulphate i cadmium has beenindicated conventionally v in Fig. 1.

If any other finish, than white cadmium I color is desired,-the various shades may be obtained by superimposed coats of suitable .metal. For example, copper may be super imposed on the cadmium coating, as indicated conventionally in Fig. 2. The cadmium coating may be oxidized by well known methods, as for example, by treatment with analkaline solution of whitearsemc.

In my opinion the success of an unalloyed v cadmiumcoating for the revention of corrosion of aluminum an closely related metals is to be ascribed to the fact that in a salt atmosphere or solution substantially no difl'erence of potential exists between the aluminum and the cadmium. The high resistance to atmospheric corrosion of cadmium keeps the cadmium coating intact and protects the surface of the foundation metal.

I mean by the appended claims to cover not only my invention as applied to articles containing aluminum, but also other metals subject to corrosion in the same electrolytic series, as for example, metallic. articles containing or consisting of magnesium. What I claim as new and desire to secure byLetters Patent of the United States, is-: 1. An article -of manufacture comprising a non-ferrous metal, which in a salt solution is adjacent to cadmium in electrolytic potential and a corrosion resisting coating thereon comprising metallic cadmium.

2. An article of manufacture consisting largely of aluminum and a corrosion-resisting coating thereon containing cadmium.

3. An article of manufacture comprisin 6 an alloy of aluminum and an unalloye coating thereon of cadmium of the order of about one mil in thickness.

4. An article of manufacture consisting largely of aluminum and an electrodeposited coating of cadmium thereon whereby said 10 article is rendered resistant to the corrosiveinfluence of a salt atmosphere.

In witness whereof, I have hereunto set my hand this 16th day of June, 1922.

CHARLES E. JONES. 

